The uninterrupted flow of cooling water through marine combustion engines used for propulsion or to generate electrical power is essential to their operation. Even brief failure of cooling water flow through a marine engine can cause overheating and resultant engine damage or failure. Failure of cooling water flow is nearly impossible to avoid however, because most marine engine cooling systems rely on sea or lake water, drawn into the system via intake ports or a sea cock, as a heat transfer medium for cooling the engine. Although this design provides an unlimited supply of cooling water, there is a significant chance that waterborne debris, seaweed, dirt or dissolved minerals will foul the intake port, clog internal channels in the cooling system, damage the impeller of the cooling system pump, or damage other types of water pump mechanisms (such as piston or diaphragm based pumps), all leading to cooling system failure.
When fouling or clogging of a marine engine cooling system occurs, the flow of cooling water through the engine becomes reduced, or shuts off completely, leading to overheating and potential damage to or failure of the engine. A reduction of cooling water flow can also create a powerful vacuum in the pipes and hoses which carry water from the water intake port to the water pump and engine, resulting in the collapse or rupture of these pipes or hoses. This problem is particularly troublesome in wire reinforced rubber hoses with an internal rubber liner, because the internal liner can collapse due to a vacuum, yet the external appearance of the wire reinforced shell remains unaffected, making it difficult to identify or locate the problem. To prevent these effects, the operator or engineer of the vessel must be able to quickly ascertain whether impairment or failure of the cooling system has occurred, in order to restore cooling water flow through the engine promptly before overheating damage can result.
While it is known to monitor marine engine overheating using temperature sensors, such devices do not indicate whether the overheating is due to cooling system failure, or is attributable to some other potential cause, such as increased engine load. Engine overheating due to cooling system failure almost certainly results in engine damage, whereas other overheating causes are typically less drastic, and often harmless, in their effects. Consequently, the inability to distinguish among causes of overheating renders troubleshooting more complicated and time consuming, and can result in unnecessary alarm over innocuous overheating events, or inattention to serious overheating problems.
More importantly, it is generally ill-advised to rely on engine temperature sensors to monitor cooling system failures, because engine damage can occur so rapidly after cooling failure that sensors may not register the problem until it is too late to avoid engine damage.
The poor reliability of engine temperature sensors for monitoring marine cooling system function is widely recognized. To overcome this problem, most marine engine operators currently monitor their cooling system's function directly, by visually inspecting the output of cooling water from the engine's exhaust port. This typically requires that the operator leave the helm of the vessel, walk to the stern of the vessel, and peer over the rail to view the exhaust port. These activities result in obvious personal and traffic safety hazards, regardless of whether or not a crew member is available to assume the operator's duties during the inspection. Furthermore, the vessel's cooling water exhaust port is often not observable due to rough waters, darkness, or physical obstructions, such as a stern mounted swim step, all of which impair the operator's view. Likewise, the inspection may be omitted due to operator inadvertence or activity conflicts. Lastly, visual inspections of cooling system function are by nature highly subjective and prone to inaccuracy. Low to intermediate cooling water flow levels may be interpreted by an inexperienced crew member as adequate, even though such levels may actually reflect critical impairment of the cooling system.
The integrity of the cooling water pump impeller, and other types of water pump mechanisms, is critical to effective operation of the cooling system. Preventative maintenance is currently the only reliable means to insure the impeller or pump remains functionally intact. Impellers and water pumps are periodically replaced at considerable expense for fear that they may soon fail. Assuredly, impeller or water pump failure results in the immediate loss of the marine engine cooling system and almost certainly results in engine damage because its failure is often undetected at least long enough to result in extensive damage, ergo expensive repairs and downtime.
The poor reliability of bilge water pumping systems are also widely recognized. In an attempt to overcome this problem, most marine engine operators currently monitor their bilge water pumping system's function directly, by visually inspecting the output of bilge water from the vessel's bilge water outlet port. This typically requires that the operator leave the helm of the vessel, walk to the outer rail of the vessel, and peer over the rail to view the outlet port. These activities result in obvious personal and traffic safety hazards, regardless of whether or not a crew member is available to assume the operator's duties during the inspection. Furthermore, the vessel's bilge water outlet port is often not observable due to rough waters, darkness, or physical obstructions such as hull curvature, all of which impairs the operator's view. Likewise, the inspection may be omitted due to operator inadvertence or activity conflicts. Lastly, visual inspections of bilge water pumping system function are by nature highly subjective and prone to inaccuracy. Low to intermediate bilge water flow levels may be interpreted by an inexperienced crew member as adequate, even though such levels may actually reflect critical impairment of the bilge water pumping system. Pump vibration and noise may also indicate the operation of the bilge water pumping system; however, this is a subjective observation and does not indicate how well the system is working, or if any bilge water is actually being pumped at all. Also the vessel operator may not be aware of the immediate need for bilge water pumping. Bilge water pumping systems often activate and operate automatically, but can also be activated and operated manually.
Bilge water pumps can use impellers, diaphragms, or pistons as the pumping mechanism, and all of these need to be monitored to evaluate their long term performance. Failure of the bilge water pump is nearly impossible to avoid, because the water extracted from the vessel by the bilge pump often contains debris and contaminants generated by the vessel itself, or objects or dissolved minerals present in water which leaks into the vessel. Consequently, bilge water pump intake ports and outflow pipes need frequent inspection and cleaning, and bilge pumps themselves need routine maintenance and replacement.
The integrity of the bilge water pump is critical to effective operation of the bilge water pumping system. Preventative maintenance is currently the only reliable means to insure the impeller or water pump remains functionally intact. The bilge pump mechanism is periodically replaced at some expense for fear that it may soon fail. Assuredly, pump failure results in the immediate loss of the bilge water pumping system and thus results in the inability to remove accumulated bilge water at perhaps a vital time.
The pumping of bilge water is a critical process on board a marine vessel. The accumulation of water on a vessel for any reason--hull leaks, rain, cooling system malfunction or foul weather--will likely result in damage or in an extreme case, sinking of the vessel. Also, a long term increase in the rate at which water is monitoring bilge water pumping system function which employs direct monitoring of bilge water outflow through the bilge water pumping.
A need also exists for a method and apparatus for directly monitoring bilge water outflow in a bilge water pumping system, which provides timely detection of bilge water pumping system impairment to allow the vessel operator to take corrective action against leaking before water damage or sinking occurs.
An additional need exists for the monitoring of the long term performance of the bilge water pumping system by measuring the water outflow flow rate. Small changes in flow rate are indicative of the need for inspection or replacement. If a reliable assessment of bilge pump integrity was available, then a boat operator or engineer could accurately determine the functional efficiency of the bilge pump during normal operations. With this information, a boat operator or engineer could safely approach, or even safely exceed, the advertised service life of the bilge pump, as long as the biloge pump still functioned at an acceptable level of efficiency.
A further need exists for the monitoring of total bilge water effluent. The increase over time of the amount of bilge water pumped from the vessel can be indicative of a worsening leak in the vessel hull.
A related need exists for a method and apparatus for monitoring marine cooling system function which distinguishes cooling system impairment from other potential causes of marine engine overheating.
A need also exists for a method and apparatus for monitoring marine cooling system function which employs direct monitoring of coolant water flow through the cooling system.
An additional need exists for a method and apparatus for directly monitoring coolant water flow through a marine cooling system, which provides timely detection of cooling system impairment to allow the vessel operator to take corrective action against overheating before engine damage or failure occurs.
A further need exists for the monitoring of the long term performance of the impeller or other pump mechanism for the cooling water system. Small changes in flow rate are indicative of the need for inspection or replacement, and under normal operation, the service life of the impeller, or other water pump mechanism could be safely approached or exceeded if a reliable assessment of impeller, or other pump mechanism integrity was available.